Purpose: Non-small cell lung cancer (NSCLC) patients show benefit from neoadjuvant chemotherapy given before surgical resection or adjuvant chemotherapy administered after tumor resection. However, several of these patients still relapse and die with metastatic NSCLC. These relapses represent resistance of the tumors to chemotherapy. NSCLC resistance to standard taxane and platin doublet chemotherapy is a major problem. Identifying and overcoming resistance mechanisms are thus urgently needed and the focus of this research.
Methods: (A) NSCLC cell lines were exposed long term to cycles of paclitaxel + carboplatin in clinically relevant dosage ratios, to select and subsequently characterize resistant cells. (B) Subcutaneous xenografts of parental and resistant cell lines were established in NOD/SCID mice to include expression changes that are retained in vivo. (C) Molecularly and clinically annotated dataset of NSCLC patient tumors obtained after neoadjuvant taxane + platin chemotherapy (N = 66; some had long term disease free survival and some had tumor relapses) were subjected to gene expression and survival analyses.
Results and Significance: NSCLC cell lines NCI-H1299 and NCI-H1355 treated for 16-18 cycles with paclitaxel + carboplatin developed >50 fold resistance. Cells also developed cross-resistance to doxorubicin and vinorelbine. In addition, these resistant cell lines showed decreased response to docetaxel + cisplatin doublet in vivo. Consistent with the literature, cells showed increased expression of multi-drug transporter ABCB1/MDR1. This corresponded to decreased intracellular docetaxel accumulation in resistant cells. Cell line variants showed reversal in resistance when exposed to MDR1 inhibitors or with ABCB1 knockdown. Reversal in both cases was however partial, suggesting additional resistance mechanisms. This was also indicated by repeating long term drug selection in presence of MDR inhibitor, wherein cells still developed resistance. Microarray profiles of resistant cell lines suggested mRNA expression changes in stem cell pathways, epithelial-to-mesenchymal transition (EMT) genes and certain epigenetic modulators. Cross-comparison of gene hits from cell lines and xenografts yielded 14 commonly up-regulated and 21 down-regulated genes that formed a resistance signature from preclinical models. This 35-gene resistance signature could successfully classify neoadjuvant treated patient tumors into two main clusters with significant differences in tumor recurrence and cancer-free survival. Studies are underway to determine whether this signature is purely prognostic or also has a functional role in causing resistance. Such information will provide both clinically useful biomarkers to type tumor response in patients and also potentially new therapeutic targets to overcome standard taxane-platin drug resistance in NSCLC.
Citation Format: Maithili Prafulla Dalvi, Carmen Behrens, Milind Suraokar, Rui Zhong, Brenda Timmons, Luc Girard, Yang Xie, Ignacio Wistuba, John D. Minna. Developing a molecular understanding of non-small cell lung cancer resistance to standard taxane-platin chemotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3772. doi:10.1158/1538-7445.AM2014-3772